The present invention relates to intermediate transfer members, and more specifically, to intermediate transfer members useful in transferring a developed image in an electrostatographic, especially xerographic, including digital, machine or apparatus. In embodiments of the present invention, there are selected intermediate transfer members comprising a layer or substrate comprising a filled polymer, preferably a filled polyimide, and particularly preferred a fluorinated carbon filled polyimide. In embodiments, the present invention allows for the preparation and manufacture of intermediate transfer members with excellent electrical, chemical and mechanical properties, including controlled resistivity in a desired resistivity range and excellent conformability. Moreover, the intermediate transfer members herein, in embodiments, allow for high transfer efficiencies to and from intermediates even for full color images and can be useful in both dry and liquid toner development systems.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. Generally, the electrostatic latent image is developed by bringing a developer mixture into contact therewith. The developer mixture can comprise a dry developer mixture which usually comprises carrier granules having toner particles adhering triboelectrically thereto, or a liquid developer material which may include a liquid carrier having toner particles dispersed therein. The developer material is advanced into contact with the electrostatic latent image and the toner particles are deposited thereon in image configuration. Subsequently, the developed image is transferred to a copy sheet. It is advantageous to transfer the developed image to a coated intermediate transfer web, belt or component, and subsequently transfer with very high transfer efficiency the developed image from the intermediate transfer member to a permanent substrate. The toner image is subsequently usually fixed or fused upon a support which may be the photosensitive member itself or other support sheet such as plain paper.
In electrostatographic printing machines wherein the toner image is electrostatically transferred by a potential between the imaging member and the intermediate transfer member, the transfer of the toner particles to the intermediate transfer member and the retention thereof should be as complete as possible so that the image ultimately transferred to the image receiving substrate will have a high resolution. Substantially 100% toner transfer occurs when most or all of the toner particles comprising the image are transferred and little residual toner remains on the surface from which the image was transferred.
Intermediate transfer members allow for positive attributes such as enabling high throughput at modest process speeds, improving registration of the final color toner image in color systems using synchronous development of one or more component colors using one or more transfer stations, and increasing the range of final substrates that can be used. However, a disadvantage of using an intermediate transfer member is that a plurality of transfer steps is required allowing for the possibility of charge exchange occurring between toner particles and the transfer member which ultimately can lead to less than complete toner transfer. The result is low resolution images on the image receiving substrate and image deterioration. When the image is in color, the image can additionally suffer from color shifting and color deterioration. In addition, the incorporation of charging agents in liquid developers, although providing acceptable quality images and acceptable resolution due to improved charging of the toner, can exacerbate the problem of charge exchange between the toner and the intermediate transfer member.
Preferably, the resistivity of the intermediate transfer member is within a preferred range to allow for sufficient transfer. It is also important that the intermediate transfer member have a controlled resistivity, wherein the resistivity is virtually unaffected by changes in humidity, temperature, bias field, and operating time. In addition, a controlled resistivity is important so that a bias field can be established for electrostatic transfer. It is important that the intermediate transfer member not be too conductive as air breakdown can possibly occur.
Attempts at controlling the resistivity of intermediate transfer members have been accomplished by, for example, adding conductive fillers such as ionic additives and/or carbon black to the outer layer. However, there are problems associated with the use of such additives. In particular, undissolved particles frequently bloom or migrate to the surface of the polymer and cause an imperfection in the polymer. This leads to nonuniform resistivity, which in turn, causes poor antistatic properties and poor mechanical strength. The ionic additives on the surface may interfere with toner release. Furthermore, bubbles may appear in the conductive polymer, some of which can only be seen with the aid of a microscope, others of which are large enough to be observed with the naked eye. These bubbles provide the same kind of difficulty as the undissolved particles in the polymer, namely poor or nonuniform electrical properties and poor mechanical properties.
In addition, the ionic additives themselves are sensitive to changes in temperature, humidity, and operating time. These sensitivities often limit the resistivity range. For example, the resistivity usually decreases by up to two orders of magnitude or more as the humidity increases from 20% to 80% relative humidity. This effect limits the operational or process latitude.
Moreover, ion transfer can also occur in these systems. The transfer of ions leads to charge exchanges and insufficient transfers, which in turn causes low image resolution and image deterioration, thereby adversely affecting the copy quality. In color systems, additional adverse results include color shifting and color deterioration. Ion transfer also increases the resistivity of the polymer member after repetitive use. This can limit the process and operational latitude and eventually the ion-filled polymer member will be unusable.
Carbon black particles can impart other specific adverse effects. These carbon dispersions are difficult to prepare due to carbon gelling, and the resulting layers may deform due to gelatin formation. This can lead to an adverse change in the conformability of the intermediate transfer member, which in turn, can lead to insufficient transfer and poor copy quality, and possible contamination of other machine parts and later copies.
Generally, carbon additives tend to control the resistivities. However, the required tolerance in the filler loading to achieve the required range of resistivity is extremely narrow. This, along with the large xe2x80x9cbatch to batchxe2x80x9d variation, leads to the need for extremely tight resistivity control. In addition, carbon filled polymer surfaces have typically had very poor dielectric strength and sometimes significant resistivity dependence on applied fields. This leads to a compromise in the choice of centerline resistivity due to the variability in the electrical properties, which in turn, ultimately leads to a compromise in performance.
Therefore, there exists an overall need for an intermediate transfer member for use in both dry and liquid toner systems, which provides for increased toner transfer efficiency and a decrease in the occurrence of charge exchange. More specifically, there exists a specific need for an intermediate transfer member having controlled resistivity in a desired range to neutralize toner charges, thereby decreasing the occurrence of charge exchange, increasing image quality and preventing contamination of other xerographic members. In addition, there exists a specific need for an intermediate transfer member which has an outer surface having the qualities of a stable resistivity in the desired resistivity range and, in embodiments, has improved conformability and low surface energy properties of the release layer.
The present invention provides, in embodiments, an intermediate transfer member comprising a fluorinated carbon filled polyimide substrate.
The present invention further includes, in embodiments, an intermediate transfer belt for transferring a liquid image having at least a liquid carrier with toner or solid particles dispersed therein from a member to a substrate, comprising a fluorinated carbon filled polyimide substrate, and having thereon a fluoroelastomer intermediate layer, and positioned thereon an outer silicone rubber release layer.
In addition, the present invention provides, in embodiments, an apparatus for forming images on a recording medium comprising: a charge-retentive surface to receive an electrostatic latent image thereon; a development component to apply toner to said charge-retentive surface to develop said electrostatic latent image and to form a developed image on said charge retentive surface; an intermediate transfer member to transfer the developed image from said charge retentive surface to a substrate, wherein said intermediate transfer member comprises a fluorinated carbon filled polyimide layer; and a fixing component.